The present invention relates generally to a welding-type system and, more particularly, to a wire feeder having lower minimum input voltage requirement. Specifically, the invention is directed to a power supply that maintains power supply to controlled electronics for implementing a welding-type process when output voltage falls below 15 volts.
Wire feeders are typically used to feed metal wire into a weld during a welding process such as Gas Metal Arc Welding (GMAW) and other welding processes. Typical wire feeders have a drive roller assembly for driving the metal wire feed from a feed spindle through a welding gun for introduction to the weld. Power is supplied to the drive roller assembly by a welding power supply via a weld cable. The amperage or current generated by the power supply governs the speed in which the metal feed is fed to the weld, or the wire feed speed (WFS). Generally, the higher the amperage supplied to the wire feeder, the greater the WFS. Conversely, if voltage is used to govern the WFS, the lower the voltage, the lower the WFS. Accordingly, the speed by which the wire feeder supplies the metal filler to the weld is a direct function of the power delivered to the wire feeder and therefore, the weld. Furthermore, by adjusting the WFS and holding either voltage or current constant, the adjustment to the WFS causes the non-constant value to be adjusted accordingly.
The thickness of the metal being welded determines the power required at the weld and thus the WFS necessary to deliver that power. A thicker metal requires higher power to effectively weld. The wire feeder includes a wire feed control to control the power delivered to both the wire feeder and the point of the weld. Typically, the Wire feed control allows the welding system to operate in at least one of two modes: constant voltage (CV) or constant current (CC).
Should the user choose CV mode, as is most common, a user selected voltage is required. The voltage is an indication of the voltage desired at the point of the weld and is held constant by the power supply. It is also necessary to select an initial WFS. The WFS indicates the speed with which the metal filler is delivered to the point of the weld but when the mode is CV, also corresponds to an output current. By holding the output voltage constant, the user can manipulate the output current by adjusting the WFS. Since the WFS is directly proportional to the current delivered to the wire feeder and point of the weld, the higher the WFS, the greater the current delivered to the weld. However, should the user choose CC the user input current is held constant and the wire feeder can adjust the WFS to obtain the desired voltage at the weld. In this case, the user must lower the WFS in order to raise the voltage at the weld or raise the WFS to lower the voltage at the weld.
Some wire feeders are powered or work off the arc voltage of the welding system. With these wire feeders, which are commonly referred to as “voltage sensed wire feeders” and are operable in either a CC or CV mode, arc voltage from a point at the weld area is input to a power conditioning or power converting assembly. The power converting assembly is designed to provide a secondary power that is usable by the electronic components of the wire feeder. To maintain consistent operation of the wire feeder, the arc voltage must be sufficient to drive the power converting assembly. Otherwise, the power converting assembly may be unable to supply sufficient secondary voltage to power the wire feeder's electronic components. Customarily, the power converting assembly is unable to output sufficient secondary voltage if the arc voltage falls below approximately 15–16 volts. As a result, the components of the wire feeder are not sufficiently powered and cease to function properly. That is, there is a drop-out of weld power when the arc voltage falls below 15 volts thereby causing the arc voltage to be the limiting factor of the system rather than the components of the wire feeder.
It would therefore be desirable to design a power supply that supplies sufficient secondary power to a wire feeder and other components of a welding system when arc voltage is below 15 volts thereby increasing the range of operability of the welding system.